Production of a concentrated coffee extract includes steps of roasting, grinding, extraction and concentration. Various processes are proposed in order to minimize the loss and change of the aroma component in each step. An excessive oil content undesirably promotes the deterioration of the concentrated coffee extract and causes separation and precipitation of coagulates during a long storage period. Therefore, processes for suppressing the elution of such an excessive oil content are being studied.
For example, for recovering the aroma component released at the time of grinding (hereinafter, occasionally referred to as the “grinding aroma” or “aroma component”), a process of cooling and condensing the aroma component using liquid nitrogen to recover the aroma component is proposed (see, for example, U.S. Pat. No. 5,323,623). However, in consideration of the industrial-scale production, it is not preferable to use low temperature solvents such as liquid nitrogen, liquid ammonia or the like from the viewpoint of the cost.
A process of capturing the grinding aroma in a solvent by grinding the roasted coffee beans in a wet manner to recover the grinding aroma is also proposed (see, for example, Japanese Laid-Open Patent Publication No. 2000-333612, and Japanese PCT National-Phase Laid-Open Patent Publication No. 2002-511236). However, the process described in Japanese Laid-Open Patent Publication No. 2000-333612 uses drip brewing for extracting the roasted coffee beans. The drip brewing, which requires a long time to separate the liquid phase from the solid phase and thus causes quality deterioration, is not preferable for industrial production. Japanese Laid-Open Patent Publication No. 2000-333612 also describes a process of suppressing the elution of an excessive oil content by limiting the grinding particle size to a specific range. However, merely controlling the grinding particle size results in a larger amount of oil content being eluted than in the concentrated coffee extract produced by a counter-current multi-stage extraction method using a fixed bed extraction column (i.e., a commercially available concentrated coffee extract; hereinafter, occasionally referred to as the “column-extracted concentrated coffee extract”). Thus, this process cannot sufficiently suppress the elution of the oil content. Since the amount of eluted coffee oil increases in accordance with the roasting degree of the coffee beans (especially in the case of deep-roasting and dark-roasting), it is difficult to suppress the elution of the oil content by merely controlling the grinding particle size.
The process described in Japanese PCT National-Phase Laid-Open Patent Publication No. 2002-511236 adopts slurry extraction using stripping treatment as a process for extracting the roasted coffee beans. This publication describes that the slurry obtained by the stripping treatment is transferred to an extraction system, made thermally soluble, and then concentrated. However, the publication provides no description on a method for separating a liquid extracted after the slurry is made thermally soluble from the extracted residue, or on the clarification of the extracted liquid. The slurry extraction has an advantage of capable of efficiently recovering the grinding aroma but also has a problem of easily allowing an excessive oil content to elute. Japanese PCT National-Phase Laid-Open Patent Publication No. 2002-511236 does not provide any description on the control of the elution of such an excessive oil content.
For preventing the deterioration or loss of the aroma component at the time of grinding, a process of recovering the aroma component in advance before the extraction and then adding back the recovered aroma component after the extraction and concentration is known (see Japanese Laid-Open Patent Publication No. 4-287638 (patent family: U.S. Pat. No. 5,225,223) and Japanese PCT National-Phase Laid-Open Patent Publication No. 2003-507047 (patent family: U.S. Pat. No. 6,455,093)). For preventing the loss of the aroma component at the time of concentration, a process of adding the initially evaporated portion of the condensed water at the time of vaporization and concentration back to the concentrated extract is known (see Japanese Laid-Open Patent Publication No. 58-175441). However, these patent publications describe a process for producing powdered coffee, and so do not mention technological problems regarding clarification of the concentrated coffee extract, and control or prevention of precipitation of the oil content, or do not mention any means for solving the problems. In addition, the component which is added back is limited to a water-soluble component. There is no description regarding adding back an oil-soluble component.
For coffee drinks containing a dairy component, cold sweets such as ice cream and the like, and desserts such as pudding and the like, it may be occasionally preferable to contain a large amount of oil in the extract in order to enrich the flavor or thickness of taste of coffee. Therefore, a process of extracting a coffee extract by fine-grinding the roasted coffee beans such that the average particle diameter is less than 200 μm is disclosed (see Japanese Laid-Open Patent Publication No. 11-75694). However, event this process cannot sufficiently control the coffee oil content in the concentrated coffee extract, or cannot control the oil content in accordance with the quality or the roasting degree of the raw material or the application. Further, when the coffee beans are fine-ground in order to obtain a large amount of oil, there occurs a problem that the elution of excessive astringency or bitterness cannot be avoided.